The invention relates to a steam iron having a water tank, a vaporization chamber and a drip valve for supplying water from the water tank to the vaporization chamber.
For steam ironing, in the case of steam irons operating on the drip principle, a specific quantity of water is supplied from the water tank to the steam or vaporization chamber provided in the sole of the iron via a drip valve. Because of the nature of the material being ironed and the contact pressure, the steam generated in the steam chamber during the steam ironing operation cannot escape unobstructed from the steam channels opening out on the sole of the iron into the atmosphere and consequently pressure builds up in the steam chamber. This pressure affects the quantity of water flowing out of the drip valve into the steam chamber and consequently the quantity of steam escaping from the steam holes in the sole of the steam iron. The pressure in the steam chamber is dependent on the permeability of the material being ironed and the pressure with which the iron is pressed on to the material. The higher the pressure in the steam chamber, the less water flows out of the drip valve into the steam chamber and the less steam is released from the steam escape holes.
In order to equalize the pressure difference within the steam chamber and the inside of the tank, it has already been proposed that the tank and steam chamber be connected to each other by means of a pressure equalization tube (U.S. Pat. No. 2,892,272). This device is supposed to ensure that the same quantity of steam always leaves the steam escape holes, dependent only on the water level in the tank. However, equalization of the quantity of steam released from the sole is not the only feature necessary to ensure good ironing results. It is of particular importance that, depending on the density and type of fabric being ironed and the sole pressure on the material, different quantities of steam are required, while without any bearing pressure the minimum possible quantity of steam should be generated. Adaptation of the quantity of steam to the counterpressure acting on the sole or the steam escape holes provided therein is not possible with the known pressure equalization means. Furthermore, the steam may condense in the pressure equalization tube, with the condensation being deposited in the pressure equalization tube, which in turn may cause blockage of the tube. Such blockages will render the desired pressure equalization ineffective.